Clostridium difficile bacteria can cause severe, sometimes fatal colitis in horses. When a horse develops severe diarrhea (particularly if blood is present), C. difficile might be suspected, but veterinarians must confirm the infection to make sure they treat the the right organism. Toward that end, Carlos Medina-Torres, MV, MSc, a DVSc candidate at the University of Guelph in Ontario, Canada, presented a study evaluating the performance of the C. difficile TOX-A/B II ELISA test in horses at the 2008 American Association of Equine Practitioners convention, held Dec. 6-10 in San Diego, Calif.

C. difficile-associated disease is on the rise, said Medina-Torres. "This increase is responsible for increased morbidity (illness) and a substantial economic burden due to excess mortality and longer hospital stays," he commented. "There may be more pathogenic strains emerging." He estimated that severe equine cases cost about $3,000 or more to treat ($7,000 is typical for treating humans).

Medina-Torres reported the ELISA test is widely used in horses, but its performance hadn't been validated. It's very sensitive and specific for humans and pigs, but not for dogs. Thus, his group set out to validate the test. They found that the ELISA test had a sensitivity of 84%, a specificity of 96%, and good agreement (93%) with the "gold standard" cell cytotoxicity assay.

"Our conclusions were that the test is a reliable, practical (costing less than $10 per sample) test for the clinical diagnosis of C. difficile-associated disease in horses," Medina-Torres summarized